AquaClear Bio Max Inserts increase the biological filtration efficiency of your aquarium filter while enhancing its ability to reduce harmful ammonia and nitrites. These highly porous ceramic rings provide maximum surface area to facilitate the growth of beneficial bacteria. These bacteria break down toxic water contaminants and help to create a clean healthy aquatic habitat for your aquarium fish. Expands biological capacity of aquariums Provides optimal living conditions for beneficial bacteria Enhances ammonia and nitrite reduction Safe for fresh and saltwater use Sizing Sized to fit AquaClear Aquarium Filters. Size 20 5 20 gallon aquariums Size 30 10 30 gallon aquariums Size 50 20 50 gallon aquariums Size 70 40 70 gallon aquariums Size 110 60 110 gallon aquariums